Some RRDtool general questions

ivanatora · 11-19-2004, 07:36 AM

I'm trying to graph the temperature in one of the nearest cities to me. I get the data via an uploaded file, which I download once pre hour. I parse it and get the temperature in gradus Celsius. At that point I could make a MRTG graph, that shows the temperature's change, but it wont show the negative numbers (it gets really cold out there, so it IS a problem

)
RRDtool is the solution for me. I've read the manual (well.. a big part of it ^_-) but can't get some things. I need a database which holds data.. ok. I need my data to be GAUGE and to be updated once per hour. So I did the following:
rrdtool create temperatura.rrd --start 1100864907 DS:temp:GAUGE:600:U:U RRA:AVERAGE:0.5:1:24
I'm updating the database via that (put in /etc/cron.hourly):

Code:

TEMP=`cat /root/weather/LBPD.TXT | grep emper | awk '{print $4}' | cut -d"(" -f2`
TIME=`date +%s`
rrdtool update /var/www/htdocs/rrd/temperatura.rrd $TIME:$TEMP

And finally, I'm drawing the graph via that:
rrdtool graph temp.gif DEF:mytemp=temperatura.rrd:temp:AVERAGE LINE2:mytemp#FF0000

I don't know if all these things are right. I want the graph to be colored in blue if the temperature drop below zero, and red if positive. And I'm not sure if that "RRA:AVERAGE:0.5:1:24" is right.. didn't succeed to catch the meaning in the manual.
Some help here?

ivanatora · 11-19-2004, 11:11 AM

Ok, after a couple of hours troubles and changes, I've set up all things exept one. If I put the job in the crontab it doesn't update the database. (After that I see only 'nan's with rrdtool fetch)
Here is the main script that is run every 5 mins:
/var/www/htdocs/rrd/rrdtemp.5min

Code:

TEMP=`cat /root/weather/data.old | grep emper | awk '{print $4}' | cut -d"(" -f2`
TIME=`date +%s`
rrdtool update /var/www/htdocs/rrd/temperatura.rrd -t temp $TIME:$TEMP
cd /var/www/htdocs/rrd/
sh drawgraph > /dev/null

Here is /var/www/htdocs/rrd/drahgraph:

Code:

rrdtool graph -v "Celsius" temp.png DEF:mytemp=temperatura.rrd:temp:AVERAGE LINE2:mytemp#FF0000 -w 700 -h 140 -t "Temperatura" -a PNG

And here is the look of my crontab:
*/5 * * * * /var/www/htdocs/rrd/rrdtemp.5min > /dev/null
The crontab doesn't do his job, though. If I manualy run rrdtemp.5min everything is ok, but if I let the cron do that I get only 'nan's via rrdtool fetch, and nothing drawed on the image.

ivanatora · 11-19-2004, 05:00 PM

Hm, strange.. I left it in crontab and went out for a few hours. Now I'm home and checking the database (rrdtool fetch) show me only 'nan's. Well I supposed that. But after I update it manualy, there are only 'nan's again :/ No sign from a fixed value. I checked the data source, it is up, and working. The trouble is only in updating the database.
Any ideas?...

ivanatora · 11-19-2004, 05:13 PM

I removed "-t temp" from the command that updates the database and it is filling up normaly again. Manual. I'll see if now crontab works ..
Wow, maybe I'm the only one around that have rrdtroubles ;] At the end from this thread a good guide could be made ;]
I maybe should stop asking here for any little trouble I met. Just now I plan a fine rest ..

ivanatora · 11-20-2004, 05:26 AM

This morning...
No, the crontab again doesn't update the DB, and I manualy _can't_ update it :/ Give me a hand, ppl, I'm flashing the red light by now ...

ivanatora · 11-20-2004, 01:15 PM

I think I found the answer (finally!).
Just wrote the full path to the database and the rrdtool binary in the scrip, not using cd /var/www/htdocs/rrd/.